1. Field of the Invention
In at least one aspect, the present invention relates generally to spray formed articles and, more specifically, to a method of making a spray formed article.
2. Background Art
It is known to make spray formed articles such as a spray formed tool. For instance, in spray forming a tool, metal is sprayed onto a ceramic pattern to form the desired tool. The ceramic pattern is essentially the reverse of the desired tool to be produced. Typically, a ceramic slurry is poured onto a master model and solidified to form the ceramic pattern. When solidification is complete, the resulting ceramic pattern is put through a series of heat cycles and becomes the receptor onto which metal is sprayed to form a deposit in the shape of the desired tool.
One typical spray forming process comprises wire-arc thermal spraying. In a common type of wire-arc spraying, electric current is carried by two electrically conductive, consumable wires with an electric arc forming between the wire tips. A high-velocity gas jet blowing from behind the consumable wire tips strips away the molten metal, which continuously forms as the wires are melted by the electric arc. The high-velocity gas jet breaks up or atomizes the molten metal into finer particles to create a distribution of molten metal droplets. The atomizing gas then accelerates the droplets away from the wire tips towards the ceramic pattern where the molten metal droplets impact the ceramic pattern to incrementally form a deposit in the shape of the desired article.
The desired article is then removed from the ceramic pattern. The removal is typically accomplished by cutting off the perimeter of the metal deposit with a high pressure waterjet, chiseling off the majority of the ceramic pattern and then using a glass bead blaster to remove the residual ceramic from the surface of the desired article. In the case of a tool, the completed tool is then mounted and used to produce parts in conventional stamping, die casting, molding, or other tool-usable processes.
Although the above process for making a spray formed article has worked well, it suffers from the disadvantage that it can take a considerable amount of time to remove the ceramic pattern from the spray-formed article. Another disadvantage of the above process is that the ceramic pattern can be relatively time consuming and costly to make. Therefore, there is a need in the art to produce patterns for a spray formed article that can be made less time consuming and costly than other prior art processes.
Accordingly, in at least one embodiment, the present invention comprises a method of making a spray formed article. The method includes the steps of providing a sand pattern that has an inverse of at least a portion of the surface of the spray formed article. The sand pattern is formed from a sand molding composition that comprises refractory material and binder. The refractory material comprises at least about 15 weight of percent alumina, based on the total weight of the sand molding composition. The method also includes the step of spraying metallic material toward the sand pattern to form the spray formed article.
In another embodiment of the present invention, the present invention comprises the step of providing a sand pattern that has an inverse of at least a portion of the surface of a desired spray formed article, wherein the spray forming pattern comprises the cured product of a sand molding composition comprising refractory material and an inorganic, water-soluble binder. In this embodiment, the present invention also comprises the steps of spraying metallic material against the sand pattern to form a desired spray formed article on the sand pattern and separating the sand pattern from the desired article by exposing the sand pattern to water.
In another embodiment of the present invention, the present invention comprises the step of providing a sand pattern that has an inverse of at least a portion of the surface of a desired spray formed article, wherein the spray forming pattern comprises the cured product of a sand molding composition comprising refractory material present in the sand molding compound in an amount of about 75 to 98 weight percent, based on the total weight of the sand molding composition, an inorganic, water-soluble binder present in the sand molding composition in an amount of about 2 to 25 weight percent, based on the total weight of the sand molding composition, and catalyst present in the sand molding composition in an amount of about 0.2 to 2.5 weight percent, based on the total weight of the sand molding composition. In this embodiment, the refractory material has an average particle size of about 25-400 microns and comprises silica sand and at least about 15 weight percent alumina, based on the total weight of the refractory material. In this embodiment, the present invention also comprises the steps of spraying metallic material against the sand pattern to form a desired spray formed article on the sand pattern and separating the sand pattern from the desired article by exposing the sand pattern to water.
One advantage that can be found in at least one embodiment of the present invention is that a method is provided for making a spray formed article that can be made less time consuming and costly than other prior art processes.
Another advantage that can be found in at least one embodiment of the present invention is that a method is provided for making spray formed articles that can have better metal adhesion to the spray forming pattern than other prior art processes.
Another advantage that can be found in at least one embodiment of the present invention is that a method is provided for making spray formed articles that can be removed from the spray forming pattern more easily than other prior art processes.
Other features and advantages of the present invention will be readily apparent from the following detailed description taken in conjunction with the accompanying drawings.